Fetal Pig Anatomy Dissection
Materials:
Scissors
Scalpel
Dissecting tray
Dissecting probe
Dissecting pins
Goggles
Lab aprons
Metric ruler
String
Procedures:
External Anatomy
 Determine the sex of your pig. Both sexes have a double row of nipples along the ventral body surface therefore;
these structures will not help you determine sex. A male pig has a small genital opening on the ventral surface
below the area where the umbilical cord enters. A female pig has a vaginal opening next to the anus. These two
openings are found under the pig’s tail. A male pig has only the anal opening. If your pig is female, you should
also note that urogenital papilla is present near the genital opening.
 Gestation (length of internal development) for the fetal pig is 112-115 days. The length of the fetal pig can give
you a rough estimate of its age.
11 mm - 21 days
17 mm - 35 days
2.8 cm - 49 days
4 cm - 56 days
 Familiarize yourself with the external anatomy of the pig.
22 cm - 100 days
30 cm – “birth”—old enough to have been
delivered
Head
Thorax
Abdomen
Forelimb
Hind limb
Umbilical cord
Tail
Neck
 With scissors, make a 3-cm incision in each corner of the pig's mouth. Your incision should extend through the
jaw. Spread the jaws open and examine the tongue. Be careful of the sharp canine teeth in the mouth! Observe
the ridged palate on the roof of the mouth. The front part of the palate is the hard palate, while the posterior part
is the soft palate. Examine the tongue and note tiny projections called sensory papillae. Next, locate the teeth of
the pig. Canine teeth are longer for tearing food, while incisors are shorter and used for biting. Pigs are
omnivores, eating plants and animals.
 Locate the epiglottis, a cone-shaped structure at the back of the mouth. Above the epiglottis, find the round
opening of the nasopharynx. This cavity carries air from the nostrils to the trachea, a large tube in the thoracic
which supplies air to the lungs.
 Under the epiglottis is a slit. This slit is the glottis which is the opening to the trachea. Above the glottis, find the
opening to the esophagus. This appears as a horizontal slit.
 The openings at the most anterior end of the snout are the nares. As in the frog, these structures allow air to pass
in and out of the nasal chamber.
 Familiarize yourself with the inside of the pig's mouth.
Tongue
Esophagus
Epiglottis
Nasopharynx
Hard palate
Soft palate
Glottis
Nares
Sensory papillae
Canine teeth
Incisor
 Clean up your materials and work area. Put the pig in a zip-lock plastic bag. Label your bag with your names.
Clean and return your lab equipment and pig, wash your table and then thoroughly wash your hands with soap.
Internal Anatomy
 Be sure to wear your lab apron and eye cover. Obtain your dissecting equipment and pig. Place the fetal pig
ventral side up in the dissecting tray. Tie a string securely around a front limb. Run the string under the tray, pull
it tight, and tie it to the other front limb. Repeat this procedure with the hind limbs to hold the legs apart so you
can examine internal structures.
 Study the diagram below. The dashed lines show the lines of the incisions that you will make.
 With scissors, make the incisions. Be sure to keep the tips of your scissors pointed upward because a deep cut will
destroy the organs below. Also, remember to cut away from yourself.
 Spread the flaps of the body wall apart. Cut the umbilical vein which extends through the liver.
 Once the vein is cut, carefully pull the flap of skin, including the end of the umbilical cord between the hind legs.
You are now able to see the organs of the abdominal cavity.
Digestive System
 The liver is a large, lobed, brown organ occupying the top portion of the abdominal cavity.
 A coiled mass of thick, tubelike tissue is the large intestine. The mass of coiled thin, tubelike tissue is the small
intestine held together by mesentery. Above the pig’s liver is a think muscle called the diaphragm. It separates
the abdominal cavity from the thoracic (chest) cavity.
 Pull the umbilical cord down between the hind legs of your pig. The umbilical cord just after entering the pig’s
body divides into two blood vessels called the umbilical blood vessels. They lie on each side of a flat structure
called the urinary bladder.
 A saclike structure attached to the underside of the liver is the gall bladder. It is usually green and is partly
embedded in the liver. Leading from the gall bladder and extending along the underside of the liver is a tube
called the bile duct. Directly below the liver on the right (pig’s left side) is a large pouch. This is the stomach.
Leading into the top portion of the stomach is the esophagus. It appears to be rather short because it passes
upward behind the liver. Attached along the right edge of the stomach is a round, reddish organ, the spleen. The
spleen looks more like a flap lying near the stomach. A rough or coarse organ lying directly below and extending
along the underside of the stomach is the pancreas. Extending from the stomach toward the left side (pig’s right)
is a tube which is the beginning of the small intestine. This part is the duodenum. Both the pancreas and the gall
bladder empty digestive chemicals into this structure. The bile duct which leads from the gall bladder to the
duodenum should be visible. The duct leading from the pancreas is small and difficult to locate. At the junction
between the small and large intestines is a small, fingerlike projection. This structure is the cacum (our appendix).
 Push the intestines as far to your left as possible. Also, pull the urinary bladder and umbilical cord down. A tube
leading from the large intestine out of the abdominal cavity towards the pig’s tail is the rectum. The opening of
the rectum to the outside on the animal’s body is the anus.
 Familiarize yourself with the layout of the digestive system.
Liver
Large intestine
Small intestine
Cacum
Gall bladder
Stomach
Duodenum
Spleen
Pancreas
Bile duct
Rectum
Esophagus
Umbilical blood vessel
Umbilical cord
Anus
Identify the organ (or structure)
_____________________________Produces bile and detoxifies the blood.
_____________________________ The “dead end” at the junction of the small and large intestines.
_____________________________ Separates the thoracic and abdominal cavity; aids breathing.
_____________________________ Membrane that holds the coils of the small intestine in place.
_____________________________ Liquifies foods using acids and begins protein digestion..
_____________________________ The holding chamber for feces before it exits at the anus.
_____________________________ Bumpy structure under the stomach that produces insulin.
_____________________________Location where most of the chemical digestion and absorption takes place.
_____________________________ Part of the immune system that removes old red blood cells.
_____________________________ Absorbs water from the remaining indigestible food matter.
Respiratory System
 Extend the cut in your pig’s chest cavity made during the examination of the digestive system. Continue cutting
in a straight line along the middle of the chest up to the chin.
 Locate the trachea, a long tube composed of ringlike sections extending along the middle of the chest cavity.
Lying ventral to the trachea or windpipe, locate the pinkish-brown, V-shaped structure called the thyroid gland.
 Push aside muscle attached to the top portion of the trachea. A slight bulge in the trachea is the larynx or voice
box. Cut lengthwise into the larynx with scissors to expose the vocal cords.
 Locate the left and right lungs. These organs are composed of soft tissue and have many lobes which occupy
most of the chest cavity.
 Remove any tissue covering the lower portion of the trachea. The trachea branches into each lung. These
branches are the left and the right bronchi.
 Between the chest and abdominal cavity is a very thin sheetlike muscle. The muscle, called the diaghragm
separates the thoracic cavity from the abdominal cavity and it also aids in inhaling and exhaling.
 Where the bronchi enter the lungs, the bronchi again branch off into bronchial tubes. These branches continue
to branch off until they are very small and do not contain cartilage rings. They end as many small air sacs
called alveoli. Alveoli are very thin walled and are surrounded by capillaries of the lungs. It is in the alveoli
where gas exchange occurs between blood and air.
 Familiarize yourself with the respiratory system
Trachea
Larynx
Vocal cords
Diaphragm
Left lung
Right lung
Left bronchus
Thyroid gland
Right Side
Left side
Circulatory System
 Locate the heart. It is covered by a thin tissue called the pericardium. Remove this membrane to study the heart.
The coronary blood vessels are the weblike blood vessels on the surface of the heart to supply the heart tissue
with blood.
 Pigs, like all mammals, have four-chambered hearts. The right side of the heart pumps blood to the lungs, while
the left side of the heart pumps blood to all other parts of the body. Locate the right and left sides of the heart.
Separating the two sides of the heart is a muscular tissue called the septum.
 Each side of the heart has an upper and a lower chamber. Upper chambers are called atria and receive blood,
while lower chambers are called ventricles and pump blood out of the heart. Locate the right and left atria and
ventricle.
 Notice that the surface of the heart is covered with blood vessels. These are part of the coronary circulation, a set
of arteries and veins whose only job is to nourish the heart tissue. Blockage in these vessels causes heart attacks.
 Anterior to the heart, locate another large vein that enters the right atrium. This vein, the superior vena cava,
brings blood to the right atrium from the anterior part of the body.
 Now lift the heart to view its dorsal surface. Observe the inferior vena cava that carries blood from the posterior
part of the body and empties it into the right atrium.
 Find the pulmonary artery which leaves the right ventricle. After birth, this vessel carries blood to the lungs.
However, in a fetus, a shunt called the ductus arteriosus allows fetal blood to bypass the lungs and go directly to
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the aorta, the largest artery of the body. Locate the pulmonary veins that enter the left atrium. After birth, these
vessels carry oxygenated blood from the lungs to the heart.
Identify the aorta, a large artery that transports blood from the left ventricle. Many arteries that carry blood
throughout the body branch off of the
Remove the heart by severing the blood vessels attached to it.
Hold the dorsal and ventral surfaces of the heart with your thumb and forefinger and rest the ventricles on your
dissecting tray. Cut the heart into dorsal and ventral halves.
Remove any material inside the heart and expose the walls of the atria and the ventricles.
Familiarize yourself with the heart
Inferior vena cava
Superior vena cava
Aorta
Pulmonary artery
Pulmonary vein
Right atrium
Left atrium
Right ventricle
Left ventricle
Septum
Urogenital System
 Locate the kidneys and the tubes leading from the kidneys that carry urine called the ureters. The ureters carry
urine to the urinary bladder, located between the umbilical vessels.
Lift the bladder to locate the urethra, the tube that carries urine out of the body. Note the vessels that attach to the
kidney , these are the renal vessels
 Male
Find the scrotal sacs at the posterior end of the pig (between the legs), testes are located in each sac.
From each testis, find the coiled epididymis. Sperm cells produces in the testes pass through the epididymis and
into a tube called the vas deferens (in humans, a vasectomy involves cutting this tube).
The penis can be located by cutting away the skin on the flap near the umbilical cord. This tube-like structure
eventually exits out the urogenital opening, also known as the urethra.
 Female
In the female pig, locate two bean shaped ovaries located just below the kidneys and connected to the curly
oviducts.
Trace the oviducts toward the posterior to find that they merge at the uterus. Trace the uterus to the vagina. The
vagina will actually will appear as a continuation of the uterus.
 On the diagrams below of the female and male urogenital systems, label the following:
Scrotal sac
Oviducts
Urethra
Ovary
Ureter
Urinary bladder
Kidney
Uterus
Vas deferens